removal of cadmium from wastes containing cadmium

Al- Mustansiriyah J. Sci. Vol. 32, No 8, 2013

71

Removal of Cadmium Ions from Industrial Wastewater

Using Iraqi Ceratophyllum Demersum

Jameel M. Dhabab1, Kadhem A. Hussien

2 and Tarikak. Nasser

3

1,2Department of Chemistry, College of Science, Al-Mustansyria University

3Marine chemistry-Basra marine center-Basra university

Received 1/3/2012 – Accepted 27/5/2012

ABSTRACT A new simple method was developed for the removal of cadmium ions from

wastewater by using natural and modified dried leaves of (ceratophyllum

demersum) . This plant is an Iraqi spices grew on the shores of Iraqi rivers. Optimal

conditions were obtained (pH was 6, weight of adsorbent was1.5g, particle size was

300µm, temperature was30°c, contact time was 60 minute and concentration of

cadmium ions was 10 mg/L).These parameters were applied on spiked samples (50

gm./L) and proved to be efficient( 95% removal for natural and 98% for sodium

hydroxide treated modified ).A batch sorption isotherm showed that Temkin model

was dominant for natural ceratophyllum demersum but Langmuir model for

modified was the dominant. The thermodynamic parameters were given and showed

that ΔH° was endothermic-positive value, ΔG° was found (a spontaneous process-

negative value) and ΔS° was found positive value- increase of disorder of the

process. FTIR was used to identify the activity of adsorption process by knowing of

active sites on the surface of adsorbent.

INTRODUCTION Cadmium is one of toxic heavy metal that discharges from industrial

activity, considered as pollution metal ion, which can cause serious

damage to the kidneys and liver [1]. Cadmium ion has been found as a

human carcinogen [2]. The maximum permissible limits for cadmium in

drinking water were 3 -10µg/L (WHO) [3]. Cadmium is released to the

environment by different activities, such as electroplating, pigments,

plastic, battery and zinc refining industries [4,6]. In order to remove

cadmium from polluted wastewater different physical and chemical

methods were used [7]. Those methods included; precipitation [8],

cementation [9], membrane separation technique [10], ion exchange

technique [11], solvent extraction technique [12] and adsorption [13].

Conventional methods have been found with limited application due to

poor efficiency, sensitive operating, conditions and high cost of their

disposal. Adsorption was also found powerful technique for removal of

cadmium [14]. New adsorbents were found successful for removal

cadmium and were improved performance of application [15].

Agricultural wastes have been extensively used for wastewater effluent

[16,17]. The mechanism of adsorption was attributed to functional

groups present in biomass molecules such as: carbonyl, phenol, amino,

carboxyl groups, alcohols, amido, ester and other groups [18]. These

groups may bind with heavy metals to form complexes [19]. Many

Removal of Cadmium Ions from Industrial Wastewater Using Iraqi Ceratophyllum Demersum

Jameel, Kadhem and Tarikak

72

adsorbents were reported as bioasorbents which were obtained from

agricultural materials; These materials such as: saw dust [20], barks

[21,22], stems [23,24], shells [25], peels [26,27], husk [28,29], bran

[30,31] and leaves [32,33]. Despite the large number of bioadsorbents,

there are still other herbs that have not been investigated such as Iraqi

natural Ceratophyllum Demersum (NCD) and modified Ceratophyllum

Demersum (MCD). This paper is an attempt for study of parameters to

develop and new method for removal of Cd (ІІ) from wastewater.

MATERIALS AND METHODS Chemical and instrumentation;

Chemicals: Stock solution; stock solution of cadmium (1000 mg/L) was prepared

by dissolving (2.74 gm.) of analr (99.9%) (Cd (NO3)2.4H2O) (Obtained

from Fluka) in 1liter of distill-deionized water. The resulting solution

was diluted to 100 mg/l and standardized against 0.1N EDTA to obtain

the exact concentration of cadmium ion. Other chemicals are 0.1 M

HCl and NaOH, both solutions were standardized before use. All

measurements were triplicate. Blank values were considered and

subtracted from all measurements. .

Natural CeratophyllumDemersum (NCD) (dried leaves): the NCD

plants were collected from Al-Kufa River, Najaf, Iraq on October 2011.

Then washed with tap water, Then the product was dried at 80 C° for36

h and broken into many pieces into different particle size (300,500 and

700 µm) using clean mortar and pestle. Finally the dried plants stored

in clean plastic envelope.

Modified Ceratophyllum Demersum leaves (MCD): add 300 mL of

NaOH (0.1 M) to 30g of natural ceratophyllum demersum. The mixture

was heated to 120 C° for 30 min and stirred occasionally. Cool, then

separate the plant powder by filtration, and then washed with distilled

water until the washing was free of color and the final pH of effluent

was 7. The residue was dried at 50C°, overnight to avoid thermal

deactivation of the adsorbent surface [34].

Instrumentations:

All the following instruments were calibrated by using standard

solutions or reference material to obtain the satisfaction:

1- Atomic absorption spectrophotometer used was Shimadzu AA-6200.

2- FT-IR spectrophotometer – Shimadzu 6000.

3-pH meter was Research pH meter Radiometer, Cobenhagen,

Denmark.

4-Shaker was BS-11 digital, JEIO TECH, Korea.

Procedures:


73

1- Preparation of natural ceratophyllum demersum; weigh 50gm of

(NCD) and place in small beaker and washed with deionized water and

then crushed into many pieces using mortar and pestle ( particle sizes

were 300, 500, and 700um).

2- Preparation of modified ceratophyllum demersum ;weigh 30 gm

of (NCD) plant and place in small beaker. Heat to 120 c° ,and

thoroughly add 300 ml of NaOH (0.1M), then the final solution was

placed in shaker water bath for 30 min. Cool and filter , then washed

with distill-deionized water, dry overnight at 50C°. The material was

finally ready for use.

3-Prepartion of spiked wastewater; Prepare series of diluted cadmium

solutions (10-50mg/L) from stock solution .all measurements of

cadmium before and after adsorption were measured by atomic

absorption spectrophotometer (shemadzu AA 6200).

4-Batch adsorption procedures; to measure the adsorption of

cadmium ion on (Ceratophyllum demersum) different weights of

adsorbents were used at different concentration of metal ion (10-50

mg/L). All parameters were kept constant at optimum values. Measure

concentration of cadmium ion before and after adsorption by flame

atomic absorption.

RESULTS AND DISCUSSION Characterization of adsorbents

In order to evaluate the adsorption properties of ceratophyllum

demersum. FTIR was used to obtain spectra as shown in (Fig 1). This

figure gave vibration absorption bands which were identified; 3412 cm-1

for (-OH) group, 2926 cm-1

for alkyl group (-CH2-). The bands at 1660

and 1095 cm-1

were considered indicator of the presence of (c=c) and

(c-o-c) respectively [35].

Optimization of adsorption process; In order to obtain maximum

removal of cadmium ions from waste water conditions have to be found

, these are ,contact time ,pH , weight of adsorbent , concentration of

cadmium , particle size and temperature. The following are procedures

for these studies:

1- Effect of contact time; The following parameters are fixed as

follows (pH at 6, cadmium concentration at 50mg/L, weight of natural

and modified plant at 1 gm at 50ml of metal ion solution and

temperature at 30°c). The only variable in this optimization was contact

time. Use different times (30, 60, 90, and 120 min) carry out batch

adsorption of each solution and results are given in Fig. 2. It is shown

that optimal time is 120 min for both, but (MCD) is slightly higher than



74

(NCD) in removal of cadmium ions; and these results are similar to

efficiency of plant used before [36, 37].

2- Effect of pH; in order to optimize the pH, all the parameters were

fixed (amount of both adsorbents were 1gm, concentration of cadmium

was 50mg/L., time of adsorption was 1hour,).But pH was varied from 2

to 8(pH was adjusted by using buffer solution). Results are given in fig

3. pH was optimum at 6 for both (NCD) and (MCD) . At acidic pH the

adsorbent surface will be converted to carboxylate and phenolate which

give active site on the surface of adsorbent, at alkaline medium,

hydrogen ions removed by hydroxide ion, and therefore adsorption

decrease [38] .

3- Effect of weight of adsorbent; to observe the highest amounts of

adsorbent that give optimum adsorption at fixed concentration of

cadmium, temperature and time of adsorption. Variable amounts of

(NCD) and (MCD) (1, 2, 3, 4, and 5gm) at 50 ml of metal ion solution

were added independently to the reaction mixture and carry out batch

adsorption, finally cadmium was measured before and after adsorption.

Results are given in fig.4. Optimum adsorbent was found 1.5gm/50ml

for (NCD) and 1gm/50ml for (MCD).

4- Effect of concentration of cadmium ions; using optimum adsorbent

amount, pH, temperature, time of adsorption and all these parameter

were fixed to measure the efficiency of cadmium removal from

wastewater. Different concentration (10,20,30,40,and 50 mg/L) were

prepared and the adsorption process was carried out and results are

given in fig, 5. Optimum concentration was 10mg/L for (NCD), while

10-20 mg/L for (MCD). At initial concentration the ratio of metal to

adsorbent was reached maximum at 10mg/L and concentration of metal

ions above the normal value did not increase because all sites on the

surface were occupied [39].

5- Effect of particle size; particle size was considered important factor

because it is related to surface area of adsorbent, therefore it has been

studied. Fixing pH,time of adsorption, temperature, weight of adsorbent,

and initial concentration, but varying particle size (300-750 µm) , then

complete adsorption batch process and measure cadmium ion

concentration before and after adsorption . Results are given in fig 6.

Optimum particle size was found 300 for both (NCD) and (MCD).

Increase of surface area accompanied with decrease particle size but

increase particle size more than 300µm will not added more active sites,


75

because a metal ion will be saturated and adsorption will be decrease

due to desorption of cadmium [40].

6- Effect of temperature; the efficiency of adsorption of cadmium was

affected by change of temperature, therefore the effect of temperature

from 20 to 50°C was obtained by fixing of all parameters except

temperature ,and batch adsorption process was completed , .results

were given in fig 7. Optimum removal efficiency was 95% for natural

and 98% for modified at 50°c. Heating the dried plant above 50°C

resulted penetrating cadmium ion to the surface and produce swelling

[41].

Adsorption models

Adsorption process is considered important for removal of

cadmium ions, therefore batch adsorption process was carried out to

study distribution of metal ion between the liquid phase and the solid

adsorbent. The adsorption equilibrium can be expressed by one model

or many other models following isotherm pattern [42].Three different

common models of isotherm were studied (Langmuir, Freundlich and

Temkin isotherms). R2 values and slope both measured and found to be

related to Temkin isotherm model for NCD and Langmuir model for

MCD. Fig.8 and fig.9 gave linear plot, which suggested that adsorption

was Temkin isotherm for natural and Langmuir isotherm for MCD

respectively [43].

Thermodynamic Studies:

Adsorption process was found useful to calculate thermodynamic

parameters such as change in free energy ΔG°, enthalpy ΔH° and

entropy ΔS°. Using the following equations;

K= (Qe×W) / (Ce×V) ………….(1)

ΔG°= - RT ln K ………….(2)

Log K= (ΔS°/2.303R)-(ΔH°/2.303 RT) ………… (3)

ΔG°=ΔH° - TΔS° …………. (4)

As K is the equilibrium constant, Qe is adsorption efficiency (mg/g), Ce

is final concentration of metal ions (mg/L), W is weight of adsorbent

(g), V is the volume of solution (litter), T is the absolute temperature

(K°) and R is the gas constant [44, 45].

Van,t Hoff equation was used to estimate the values of ΔH° and ΔS°

from the intercept, and slope of the plot which was ln K vs. 1/T (fig.

10).Table (1) showed the thermodynamic parameters values for the

adsorption processes. From this table, adsorption process was found

endothermic (ΔH° was positive), reaction was spontaneous (ΔG° was

negative), and solid solution interface was random because ΔS° was



76

increased. The change in adsorption enthalpy was measured and found -

20 to 40 KJ.mol-1

, compared to chemisorption which was -400 and -80

KJ.mol-1

[46]. values of ΔH° physisorption was found the dominant

mechanism.

Application

From experimental results, it was clear that cadmium ions can be

removed from industrial waste using NCD and MCD at optimum

conditions. Three samples were taken from three different Iraqi

factories: Babylon batteries factory, Kufa cement factory and Babylon

tiers factory. From results, it was found that NCD and MCD gave high

efficiency (100%) for the removal of Cd ions at optimum conditions.

Results were given as in table 2. Therefore this method was

recommended for industrial application.

Conclusions:

NCD and MCD Were found successful for removal of cadmium ions

from waste water (95.3% for NCD and 98.8% for MCD). And this

percentage considered higher than other adsorbents, therefore this

method is recommended as efficient method for treatment of waste

water polluted with cadmium in spiked and real sample. The Temkin

adsorption isotherm model was better used to represent the experimental

data on NCD and Langmuir model for MCD. MCD was found slightly

higher than natural.

Table -1 : the thermodynamic parameters for adsorption process with NCD and

MCD as adsorbents Adsorbent Temperature

K°

ΔH°

KJ.mole-1

ΔG°

KJ.mole-1

ΔS°

KJ.mole-1

.K-1

Natural

ceratophyllumdemersum

303 19.496 -7684.296 25.425

Modified

ceratophyllumdemersum

303 31.177 -7695.481 25.50

Table -2: practical applications of removal of cadmium ions from Iraqi factories

wastewater by using of natural and artificial Iraqi Ceratophyllum Demersum as

adsorbents. Factory Optimum conditions Conc.

before

treatment

(mg/L)

Conc. after

treatment

(mg/L)

R%

pH Contact

time

(min.)

Temperature

(C°)

Weight of

adsorbent

(gm)

Particle

size

(µm)

Babylon batteries 6 60 30 1.5 300 0.041 0.0 100

Kufa cement 6 60 30 1.5 300 0.112 0.0 100

Babylon tiers 6 60 30 1.5 300 0.040 0.0 100


77

Fig.-1: FTIR for Ceratophyllum Demersum

Fig.-2: effect of time on adsorption process at pH=2.3, temperature=30 c°,initial

concentration=50 mg/L and adsorbent weight=1gm



78

fig.-3: effect of pH on adsorption process at time=60 min,temperature=30c°, initial

conc.=50mg/L and adsorbent weight=1 gm.

Fig.-4:effect of loading weight on adsorption process at time=60min, pH=2.3,

temperature=30 c°, and initial conc.=50mg/L


79

fig.-5: effect of initial concentration on adsorption process at

time=60min,temp.=30c°, weighe of adsorbent=1gm/50 ml of solution and pH=2.3

Fig.-6: effect of particle size on adsorption process at pH=2.3,time=60 min, initial

conc.=50mg/L,temperature=30c ° and weight of adsorbent=1gm



80

Fig.-7: effect of temperature on adsorption process at pH=2.3, time=60min,initial

conc.=50mg/L and adsorbent weight=1gm

Fig. -8:the Temkin isotherm model for natural ceratophyllum demersum (NCD) as

adsorbent


81

Fig.-9: the Langmuir isotherm for modified ceratophyllum demersum (MCD) as

adsorbent.

Fig. -10: plot of Van

,t Hoff equation for adsorption process with NCD and MCD as

adsorbents

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removal of cadmium from wastes containing cadmium

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